Shape measuring system and method

Abstract

A shape measuring system reduced in size and cost and high in the light utilization efficiency, as well as a shape measuring method, are disclosed which can measure the distance up to an object accurately without being influenced by external conditions such as a change in reflectance of the surface of the object. A semiconductor laser emits an intensity-modulated illumination light. A plane sensor detects a combined light of both a reflected light from an object and a reference light and outputs a composite light detection signal. The semiconductor laser also emits an illumination light which is a stationary light not intensity-modulated. At this time, a shutter is closed. The plane sensor detects the reflected light from the object and outputs a detection signal thereof. For the composite light detection signal a distance calculator makes correction for eliminating the influence of reflectance of the object on the basis of a detection signal of a reflected stationary light and thereafter calculates the distance up to the object on the basis of the composite light detection signal after the correction.

What is claimed is:  
     
       1. A shape measuring system wherein a light having been intensity-modulated at a predetermined frequency is emitted toward an object and the distance up to said object is determined on the basis of a phase difference between reflected light from said object and said emitted light, said shape measuring system comprising: 
       a light emitting unit that emits said light having been intensity-modulated at said predetermined frequency and emits a stationary light not intensity-modulated toward said object;  
       a reflecting member that reflects in a predetermined direction a part of said light emitted from said light emitting unit and a part of said stationary light;  
       a detecting unit that receives said light reflected from said object and also receives said light reflected by said reflecting member and outputs a composite detection signal produced by combining both said received lights and with said phase difference reflected therein, said detecting unit further receiving the stationary light reflected by said object by said stationary light and outputting a reflected stationary light detection signal, said detecting unit further receiving the stationary light from said reflecting member and outputting a stationary light detection signal; and  
       a calculating unit that, in accordance with said composite detection signal, said reflected stationary light detection signal and said stationary light detection signal, corrects for a change in reflectance of said object, and calculates said distance.  
     
     
       2. The shape measuring system according to  claim 1 , wherein said detecting unit comprises: 
       a detector that is disposed in said predetermined direction and which outputs a detection signal proportional to the intensity of incident light;  
       two shutter units disposed respectively on an optical path between said object and said detector and an optical path between said reflecting member and said detector and adapted to open and cut off said optical paths by opening and closing motions; and  
       a control unit that makes control to open or close said two shutter units, allowing said composite detection signal, said reflected stationary light detection signal and said stationary light detection signal to be outputted from said detector.  
     
     
       3. The shape measuring system according to  claim 2 , wherein, in accordance with said composite detection signal, said reflected stationary light detection signal and said detected stationary light signal, said calculating unit corrects at least for one of a change in reflectance of said object and a change in characteristics of an optical system that covers from said light emitting unit to said detecting unit, and calculates said distance. 
     
     
       4. The shape measuring system according to  claim 1 , wherein said detecting unit comprises: 
       a detector that is disposed in said predetermined direction and outputs a detection signal proportional to the intensity of incident light;  
       three shutters disposed respectively on an optical path between said light emitting unit and said object, an optical path between said object and said detector and an optical path between said reflecting member and said detector and adapted to open and cut off said optical paths by opening and closing motions; and  
       a control unit that makes control to open or close said three shutter units, allowing said composite detection signal, said reflected stationary light detection signal and said stationary light detection signal to be outputted from said detector and causing said detector to receive a reflected extraneous light reflected from said object and output a reflected extraneous light detection signal.  
     
     
       5. The shape measuring system according to  claim 4 , wherein, in accordance with said composite detection signal, said reflected stationary light detection signal, said stationary light detection signal and said reflected extraneous light detection signal, said calculating unit corrects at least for one of a change in reflectance of said object and a change in intensity of said extraneous light, and calculates said distance. 
     
     
       6. The shape measuring system according to  claim 4 , wherein, in accordance with said composite detection signal, said reflected stationary light detection signal, said stationary light detection signal and said reflected extraneous light detection signal, said calculating unit corrects at least one of a change in reflectance of said object, a change in characteristics of an optical system that covers from said light emitting unit to said detecting unit, and a change in intensity of said extraneous light, and said calculating unit calculates said distance. 
     
     
       7. The shape measuring system according to  claim 1 , wherein: 
       said detecting unit outputs, as said composite detection signal with said phase difference reflected therein, an amplitude detection signal indicating the amplitude of a combined light of both said reflected light and said emitted light and also outputs, as said reflected stationary light detection signal, a light quantity detection signal indicating the quantity of said reflected stationary light; and  
       said calculating unit calculates said distance on the basis of said amplitude detection signal and also calculates the luminance of said object on the basis of said light quantity detection signal.  
     
     
       8. The shape measuring system according to  claim 1 , wherein said detecting unit comprises a detector that outputs a detection signal proportional to the intensity of an incident light, an amplitude detecting circuit that detects the amplitude of said detection signal provided from said detecting unit, a charge storage circuit that integrates, for a predetermined period of time, an output signal provided from said amplitude detecting circuit, a by-pass line that by-passes said amplitude detecting circuit, and a switching unit that switches over said amplitude detecting circuit and said by-pass line from each other. 
     
     
       9. The shape measuring system according to  claim 8 , wherein said amplitude detecting circuit comprises a high pass filter circuit that eliminates a direct current component from said detection signal provided from said detector and outputs the thus-filtered signal, and a peak holding circuit that detects a peak of the output signal provided from said high pass filter circuit. 
     
     
       10. The shape measuring system according to  claim 8 , wherein said amplitude detecting circuit comprises a high pass filter circuit that eliminates a direct current component from said detection signal provided from said detector and outputs the thus-filtered signal, and a rectifier circuit that rectifies the output signal provided from said high pass filter circuit. 
     
     
       11. The shape measuring system according to  claim 1 , wherein said detecting unit comprises a detector that outputs a detection signal proportional to the intensity of an incident light, and an optical filter that selectively transmits a light reflected from said reflecting member or from said object. 
     
     
       12. The shape measuring system according to  claim 1 , wherein said detecting unit is provided with a common detector that receives light from said object and outputs a detection signal proportional to the intensity of the received light as well as receives light from said reflecting member and outputs a detection signal proportional to the intensity of the received light. 
     
     
       13. The shape measuring system according to  claim 1 , wherein said detecting unit comprises a first detector that receives light from said object and outputs a detection signal proportional to the intensity of the received light, and a second detector that receives light from said reflecting member and that outputs a detection signal proportional to the intensity of the received light. 
     
     
       14. The shape measuring system according to  claim 1 , wherein said detecting unit is provided with a plurality of detecting elements that are arranged in a two-dimensional manner and output detection signals proportional to the intensity of an incident light, and said calculating unit calculates distances up to a plurality of points on said object. 
     
     
       15. A shape measuring system wherein a light having been intensity-modulated at a predetermined frequency is emitted toward an object and the distance up to said object is determined on the basis of a phase difference between a reflected light from said object and said emitted light, said shape measuring system comprising: 
       a light emitting unit that emits said light having been intensity-modulated at said predetermined frequency and emits a stationary light not intensity-modulated toward said object;  
       a detecting unit that receives said light reflected from said object and also receives the emitted light and then outputs a composite detection signal produced by combining both said received lights and with said phase difference reflected therein, said detecting unit further receiving the stationary light reflected by said object by said stationary light and outputting a reflected stationary light detection signal, said detecting unit further receiving the stationary light and outputting a stationary light detection signal; and  
       a calculating unit that, in accordance with said composite detection signal, said reflected stationary light detection signal and said stationary light detection signal, corrects for a change in reflectance of said object, and calculates said distance.  
     
     
       16. A shape measuring method wherein light having been intensity-modulated at a predetermined frequency is emitted toward an object and the distance up to said object is determined on the basis of a phase difference between reflected light from said object and said emitted light, said shape measuring method comprising: 
       a first step of emitting said light intensity-modulated at said predetermined frequency toward said object, detecting said reflected light and said emitted light, combining both said lights into a composite detection signal with said phase difference reflected therein, emitting a stationary light not intensity-modulated toward said object, detecting the stationary light reflected from the object, converting the reflected stationary light thus detected into a reflected stationary light detection signal, and detecting said stationary light and converting it into a stationary light detection signal; and  
       a second step of correcting a change in reflectance of said object and calculating said distance, in accordance with said composite detection signal, said reflected stationary light detection signal and said stationary light detection signal.  
     
     
       17. The shape measuring method according to  claim 16 , wherein, in accordance with said composite detection signal, said reflected stationary light detection signal and said stationary light detection signal, said second step correcting at least one of a change in reflectance of said object and a change in characteristics of an optical system that covers from the emission of light to the detection of light, and said second step calculating said distance. 
     
     
       18. The shape measuring method according to  claim 16 , wherein said first step detects a reflected extraneous light reflected by said object and converts it into a reflected extraneous light detection signal, and said second step correcting for a change in reflectance of said object and a change in intensity of said extraneous light and calculating said distance, in accordance with said composite detection signal, said reflected stationary light detection signal and said stationary light detection signal. 
     
     
       19. The shape measuring method according to  claim 16 , wherein said first step detects a reflected extraneous light reflected by said object and converts it into a reflected extraneous light detection signal, and said second step correcting at least one of a change in reflectance of said object, a change in characteristics of an optical system that covers from the emission of light to the detection of light, and a change in intensity of said extraneous light, and said second step calculating said distance, in accordance with said composite detection signal, said reflected light detection signal and said stationary light detection signal.